Development of anti-corrosive layer on steel alloy using novel synthesized 8-hydroxyquinoline-based inhibitors: Experimental and theoretical approach

[Display omitted] •Two new synthesized 8-hydroxyquinoline derivatives were prepared and characterized.•Q-Cl and Q-NO2 compounds act as cathodic-type inhibitors.•Their performances depend on the concentrations and the donor–acceptor character.•SEM analysis confirm the formation of protective layer via adsorption of Q-Cl and Q-NO2.•DFT and DFTB calculation explain and confirm the interfacial mechanism. New and generated from freshly synthesized 8-hydroxyquinoline derivatives, namely 6-chloro-3-((8-hydroxyquinolin-5-yl)methyl)benzo[d]oxazol-2(3H)-one (Q-Cl) and 3-((8-hydroxyquinolin-5-yl)methyl)-6-nitrobenzo[d]oxazol-2(3H)-one (Q-NO2), were identified and characterized by 13C and 1H NMR spectroscopy. After this, their ability to prevent mild steel corrosion in 1.0 M HCl were examined and evaluated by electrochemical testing and surface analyses coupled with density functional theory (DFT), and density functional based tight-binding (DFTB). It is found that these substances act as the efficient defending agents and their protection increase with their concentrations and depend on their molecular structures. The best inhibition efficiencies values are about 93.59 % and 90.92 % at 10−3 M Q-NO2 and Q-Cl, respectively. Furthermore, the effect of temperature solution indicated that the 8-hydroxyquinolin derivatives take their performance of 298–328 K. In addition, the calculated activation and thermodynamic parameters indicated that they interact with the metallic surface by the chemical adsorption supported by surface analysis result using SEM/EDX analysis. These findings were explained by the Langmuir adsorption isotherm approach, indicating the formation of a monolayer by the 8-hydroxyquinoline derivatives particle on the mild steel surface. Finally, the theoretical investigations DFT/DFTB demonstrate the interaction of the site of the 8-hydroxyquinoline derivatives particles with the mild steel surface to form a protective layer.